Great to be a part of a forum such as this.
To obtain valid data of foot to "hard" ground reaction forces, force plates (strain gauge, or peizoeletric) are superb...but terribly expensive. These devices offer highly accurate centre of force (pressure) data.
Tekscan Inc. produces a product called the F-Mat which is designed to record "pressure" between foot / shod foot and floor. Novell produces the Pedobarograph.
There are limitations of such "pressure mat" systems; Since there is deformation of the mat itself, there is an attenuation of ground reaction forces (reduced).
However, since it is consistent (as the mat remains the same trial after trial) you can obtain reliable (repeatable) samples.
Using these mats you can collect multiple trials and ensemble average using other softwear (such as BioProc, or even MS EXCEL). In your work you may come across (and I know some pods / chiropodists dislike the term) "normal"
feet to use as a baseline measurement.
Untill the next generation of sensors are produced that may be the best option to obtain barefoot overground data.
I hope this helps.